Patent GB-1221781-A (GB)
Title: Extruded sheet materials and their production
Inventor: RASMUSSEN OLE-BENDT
IPC: B29C48/08
Filed: 1966-12-30
Abstract: 1,221,781. Extruded sheets of polymeric material. O.-B. RASMUSSEN. 29 Dec., 1967 [30 Dec., 1966], No. 58917/67. Divided out of 1,212,682. Heading B5B. An extruded sheet material (such as a selfsupporting film) of organic polymeric material has a disrupted layer and a continuous surface layer and a continuous surface layer on at least one surface comprising thin lamellae of a first polymeric material, the lamellae being arranged so that a portion of each is situated in a layer of the sheet where there are no connections or only disrupted connections to adjacent portions of the adjacent lamellae of the first polymeric material, whereas a substantial portion at least of the lamellae forms part of the surface layer, the surface layer consisting at any point of a large number of film formed lamellae portions laying one upon another in overlapping sandwich-like arrangement, adjacent lamellae portions in the surface layer being in intimate adherence with one another. The sheet material may have lamellae of a second polymeric material extending across the disrupted layers of the sheet and in interspersed relationship with the lamellae of the first polymeric material, the lamellae of the second polymeric material forming zones of disruption between the lamellae of the first polymeric material, the surface layer or layers being devoid of the second polymeric material. The sheet material may be made by feeding a molten first extrudable polymeric material to a multitude of first orifices opening into a collecting chamber of elongated crosssection having an outlet slot along its length, and distributed over the longitudinal dimension of the said cross-section, feeding a second extrudable material to a multitude of second orifices likewise opening into the collecting chamber and distributed over the longitudinal dimension of the cross-section thereof, the first orifices alternating with the second orifices and extending further towards at least one side of the collecting chamber than the second orifices, extruding the materials through the orifices into the collecting chamber in the form of interspersed streams, collecting the streams into the collecting chamber to form a liquid material comprising interspersed lamellae of the first and second materials, moving at least one of the walls of the collecting chamber relatively to the orifices transversely to the direction of extrusion and thereby exerting a transverse shearing effect on the lamellae during their forward travel in the direction of extrusion towards the exit slot, and disrupting the structural connections between the lamellae of the first material that are formed by the lamellae of the second material while the lamellae are either in the liquid, semi-liquid or solid state. The collecting chamber may be moved relatively to the orifices. One side of the collecting chamber may be moved relatively to the other side. The collecting chamber may narrow down in the direction of extrusion to a wide flat nozzle from which the composite structure is finally extruded and subsequently solidified by cooling. The orifices may be arranged in a circular row and the collecting chamber may be a corresponding circular collecting chamber and the collecting chamber may be rotated relative to the row. The shear may be exerted on the sides of the lamellae as they pass through the chamber as a result of their having to pass through a neck the width of which is substantially less than the length of the longest orifices. The orifices may be closely spaced elongated parallel slots forming an angle with the direction of the row. The second polymeric material may be foamed during or after the hand-off from the extruder device. The second polymeric material or the interphases between the first and second polymeric materials may be disrupted by drawing or bending. The second polymeric material may be removed at least partly by means of a solvent or by brushing.